Exemplary embodiments of the present invention relate to an apparatus, program and method to control the light propagation characteristic of an optical system to modulate the light from a light source through a plurality of light modulator elements. Exemplary embodiments further provide a light propagation characteristic control apparatus, optical display apparatus, light propagation characteristic control program, optical display apparatus control program, light propagation characteristic control method and optical display apparatus control method which extends the light-intensity dynamic range and the number of levels, and are suited to improve image quality and reduce the size and generation time of tables.
The enhancement of image quality is remarkable in the optical displays, such as LCDs (liquid crystal displays), ELs, plasma displays, CRTs (cathode ray tubes) and projectors, thus realizing the performance of resolution and color gamut nearly matched to human visual characteristics. However, as for light-intensity dynamic range, the reproduction scope lies nearly 1-102 [nit] at most while the number of levels generally is 8 bits. Meanwhile, the human sense of sight has a light-intensity dynamic range of nearly 10−2-104 [nit] at one time of visual perception and an intensity discrimination ability of around 0.2 [nit]. This, if converted into the number of levels, is considered equivalent to 12 bits. When viewing a display image on the existing optical display through the visual characteristic like this, light-intensity dynamic range looks conspicuously narrow. In addition, display image is perceivably insufficient in reality and impressions due to the shortage of intensity levels in the shadow or highlight areas.
In computer graphics (hereinafter, abbreviated as CG) for use in movies, games, etc., the movement is toward pursuing a reality of expression by providing display data (hereinafter, HDR (high dynamic range) display data) with a light-intensity dynamic range and the number of levels closely approximated to the human sense of sight. However, because of insufficient performance of the optical display to display the same, there is a problem the power of expression the CG content possessed in nature could not be exhibited to a full extent.
Furthermore, the next-generation OS (operating system) is scheduled to adopt a 16-bit color space. This drastically increases the light-intensity dynamic range and intensity levels as compared to the current 8-bit color space. Therefore, there is a desire for realizing an optical display capable of making use of the 16-bit color space.
Of the optical displays, the projection displays, such as liquid-crystal projectors and DLP projectors, are capable of making a large-screen display. Thus, those are apparatuses effective reproducing reality and expressions in the display image. In this field, the following proposal has been made in order to address or solve the above discussed and/or other problems.
Related art document JP-A-2001-100689 discloses a technology of a high dynamic range of projection display that has a light source, a first light modulator element to modulate the intensity of light over the entire wavelength region, and a second light modulator element to modulate the light intensity in the wavelength regions as to the respective wavelength regions of RGB three primary colors in the wavelength regions of light. The light from the light source is modulated by the first light modulator element to form a desired light intensity distribution, whose optical image is focused to and color-modulated on a pixel plane of the second light modulator element thereby projecting the light secondary-modulated. The first light modulator element and the second light modulator element have respective pixels under separate control on the basis of the first and second control values decided from the HDR display data. The light modulator element has a pixel or segment structure where transmissivity is under independent control, using a transmissivity modulation element capable of controlling two-dimensional transmissivity distribution. The representative examples include a liquid-crystal light valve. Meanwhile, a reflectivity modulation element may be used in place of the transmissivity modulation element, the representative examples of which include a DMD.
Now consider a case of using a light modulator element having a transmissivity of 0.2% in dark display and of 60% in light display. The light modulator element singly is given a light-intensity dynamic range of 60/0.2=300. The related art document JP-A-2001-100689 discloses a projection display capable of realizing a light-intensity dynamic range of 300×300=90000 because its light-intensity dynamic range corresponding to an arrangement of light modulator elements having a light-intensity dynamic range of 300 optically in series. Meanwhile, this concept is equivalently true for the number of levels, i.e. the 8-bit-leveled optical modulator elements optically arranged in series provide the number of levels exceeding 8 bits.
Related art document Helge Seetzen, Lome A. Whitehead, Greg Ward, “A High Dynamic Range Display Using Low and High Resolution Modulators”, SID Symposium 2003, pp.1450-1453 (2003) (hereinafter Seetzen) discloses projection displays realizing high light-intensity dynamic range and a display as disclosed in related art document JP-A-2002-99250. Both related art documents use an LCD as a first light modulator element and a modulatable lighting, such as an LED or a fluorescent lamp, as a second light modulator element.